1. Field of the Invention
The present invention is directed to a digital computer based system for diagnosing plant state and selecting information to be presented to an operator of a processing facility as he executes complex operations where the information displayed is dependant on the state diagnosed. More particularly, the invention is directed to a system in which the automatic selection of new displays of information is internally triggered by diagnosed changes in plant state where plant state cannot be unequivocally determined, and that occur as a result of the ongoing operations in which the selection process is guided by the observed sequence of such diagnosed plant state changes.
2. Description of the Related Art
U.S. Pat. Nos. 4,803,039 and 4,815,014 teach a system for computer based monitoring of the execution of complex procedures. Such a system is primarily intended for use under circumstances in which the operator of a complex processing facility is faced with an unusual, potentially adverse situation with little or no prior experience therein. Under such circumstances the operator has little choice but to rely heavily on, and follow closely, pre-planned, written procedures, defined usually by the system's designers, in order to attempt to restore critical system functions. In such cases frequent interaction between the operator and a computer based monitor of procedures execution, such as the system referenced above, is highly desirable if undesirable consequences are to be avoided.
In another class of more commonly encountered operating situations the operator of a complex processing facility performs a nearly routine operation. The start-up after shutdown of a large electrical generating plant, which might typically occur only several times a year, is representative of this class of situations. These situations inevitably involve programmed sequences of changes in the state of the plant. These changes in state may be as pervasive as changes in temperature or pressure of a working fluid or as simple as the opening or closing of a valve, or the starting or stopping of a pump. By ordinary and broadly accepted industry standards and practices such changes in state are monitored and may serve to trigger the next step in the human controlled evolution of the operation being carried out. The operator usually has had prior experience in such situations, but by reason of infrequency of occurrence the operator may not remember every detail of the sequence of operations to be performed. Such situations are not hazardous and in general pose no threat to the health and safety of either the operators or the general public. They are of interest to the owners and managers of the affected facilities because errors made in the execution of the operations can be quite costly in terms of lost production and in equipment damage resulting from incorrect sequencing of consecutive operations.
Written procedures to guide the operator in efficiently executing the desired nearly routine sequence of operations commonly exist in complex processing facilities. Nonetheless, costly operator errors occasionally occur as a result of an operator's misunderstanding of particular parts of the applicable procedure or of inadvertent omission of one or more steps of the procedure. Hence, the use of a computer based system for monitoring the execution of such nearly routine sequences of operations can again offer valuable benefits.
A computer based system for supporting plant operators in carrying out prescribed nearly routine operations is described in U.S. application Ser. No. 07/307,831. The computer based system monitors available plant instrumentation signals and processes the gathered information to detect successive changes in plant state. The system then compares the sequence of observed changes in plant state with a preprogrammed sequence and draws the operators attention to any undesirable deviations from the preplanned sequence by providing appropriate displays on a system monitor. The system requires no input from the operator when the operation underway is following the prescribed sequence and minimal input from the operator when a deviation is detected. The system internally and automatically tracks the evolution of plant states during the nearly routine operations.
In some situations, particularly those for which a clear definition of the plant state cannot be established, the systems described above may not have the capabilities to accurately choose internally among possible current plant states and therefore cannot provide the appropriate procedure related displays to the operator. This is due to the fact that the signals associated with a group of sensors whose readings define the operating state of a system may, because of instrument uncertainties, ambiguities or inadequacies, not produce a clearly identifiable pointer to a particular state. What is needed is a computer based system for machine assisted execution of process operating procedures which determines the plant state from ambiguous sensor readings, provides appropriate displays to the operator and also indicates to the operator the likely consequences of the diagnosed state.